Hi Anneleigh,
No plans to throw the old one away. I was going to try to rebuild it. Vans going in air tomorrow, will see then how bad the PO hacked the lines to do the bypass.

 

Maybe the diagrams below can help. I took the original drawing and marked what circuits are activated when the switch is in the front and rear tank positions.
The selector valve has no electrical going to it as it is pressure operated.
One way to test the sending unit is when you have the tanks down, remove the fuel pump relay and plug the electrical connector into the sending/pump unit. you can test the gauge this way by moving the arm up and down while checking the dash gauge.
Did you buy Ford pump/sending units or aftermarket? There is a procedure for checking aftermarket sending units and calibrating them to the dash gauge but I don't have it in front of me right now. Basically it involves bending the float arm if the dash gauge does not read empty when the float arm is in the bottom of the tank. I intentionally bent mine up a little more then necessary so that it shows empty before the tank is actually empty. Now I still have 4 gallons of gas in the tank when it reads empty.

I wanted to give you a better detailed post but just didn't have time! I will be sure to log in later today and check to see if you are having any problems and see if i can help. Hopefully it will all go well for you.

I used green and red to mark the circuits but you can still clearly see the letter abbreviation for the wire colors when tracing then down.


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Thank you Anneleigh, for taking the time to post these they should be very useful. I'll keep you updated. As for the pump, we'll I matched the arm to the one in the tank and that's all reinstalled already, I guess I should have checked the gauge then....dummy!!! It's a Delphi brand fuel pump, I didn't want to get the cheap one but couldn't go for the real expensive one either so I went middle of the road.

 

The old style fuel tank selector valves like someone installed on Earl91's van did require power to switch from one tank to another. The valve you and Earl91 are supposed to hove installed do not require any power. The tank selector switch on the dash will energize the pump on the selected tank and the pressure from the in-tank pump operates an internal valve within the tank selector valve. Refer to the valve diagram at the top part of the thread.

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The dash tank selector switch has 2 different electrical circuits. One is for the in tank pumps. That circuit is switched off and on by the fuel pump relay which is controlled by the EEC. The power from the fuel pump relay travels through the inertia safety switch. The inertia safety switch should open the circuit in the event of an accident. That will shut off power to the fuel pumps. That switch is located behind the passenger side kick panel.
From there the inertia, the power then goes to the dash fuel tank selector switch BUT not before first splitting off with a separate wire going to the high pressure fuel pump. The high pressure pump runs anytime the the circuit is energized regardless of which in-tank pump is selected.


The second electrical circuit that the dash mounted tank selector switch controls is for the fuel gauge. The selector switch actually switches the ground side of the gauge circuit. In the drawing below I highlighted the power circuit in red and the ground circuit in green. On our older vans Ford uses 6 volt gauges. As you see in the diagram, 12 volts si supplied through the ignition switch to the IVR and then leaves the instrument voltage regulator to feed power to the gauges at around 5 volts. So the oil, temperature, and fuel gauge have constant 5 volts supplied to them whenever the ignition switch is on. The position of the fuel tank selector switch has no affect on that as the switch is switching the ground side of the circuit.
The sending unit is a variable resistor so the resistance to ground varies according to the level of the float arm. In turn the fuel gauge varies depending on the resistance to ground. The dash tank selector switch simply switches from one sending unit to the other.

Anyway I hope it is going well and below is another diagram to go along with my post.

 

Annaleigh, thanks for the reply and more detailed info. As I expected, I hooked up the new valve, reconnected all the lines and started the van. It ran for about 3 seconds died and will not restart. Have battery on charge now, it started dying while trying to start. Here's a couple of pics of the old valve.

 

What do you think? I am guessing that the van was running before you started the work and not it is not
When you put the ignition switch in the run position, the EEC will energize the fuel pump relay for a couple of seconds to prime the system.
Do you hear any of the fuel pumps momentarily turn on when you turn the ignition switch to run?
The high pressure pump should always momentarily prime when the ignition switch is put in the run position regardless of which tank you have selected with the selector switch.

Do your wire colors match the wire colors in the diagrams I have posted?
At this point I would start by focusing on the front tank and not worry about the gauges.

Here is a easy way to jumper the fuel pump relay so that the pumps will run all the time BUT you don't want the high pressure pump sitting there running dry. You might want to unplug it while testing the low pressure in tank pumps.

Make a jumper wire to go from terminal #6 to ground and it will energize the fuel pump relay. You may or may not need to have the ignition switch in the run position, I don't remember at the moment

 

Yes, it was running before changing the valve. I am going to recheck the gas line connections, the pumps are working I can hear them, I think maybe the lines are sucking air.

 

Update, I pulled a couple of O-rings, One from the supply and one from the return. I went to the local hydraulic shop a few miles away and I bought 10 of each, that should be enough to replace all of the O-rings in all lines. I paid $4.03 for all twenty O-rings. They are Viton, so they should work fine.

On another not, I unscrewed the housing on the new switch valve, on one side there was some sort of a rubber seal or diaphragm, it looks like the gasoline ate it up, it came out in pieces. I did contact the seller from EBay, he said to take a picture and send it to them. I will, but I just learned my lesson about buying cheap crap off of EBay. I paid like $125.00 for the valve. Who knows, I might get my money returned but I doubt it. I'm going to break the old one open and see if it's gunked up and if it's cleanable. I probably won't have a chance to get back at it until this weekend.

 

There is a reason they say do not remove cup
There is no filter inside
His 90 only has one filter and the reservoir is a self switching dual tank selector
It The (crossover valve) knows which pump the fuel is coming from (using vacuum signals) and sends the return fuel back to that tank automatically
If you have somehow ruined yours you may have a hell of a time finding another at this point
Good luck

 

Well of course there's no filter in the housing it's a reservoir, but there are seals for the two plungers that are there and with very little gas getting up to the engine there had to be a reason. #1 is sucking air #2 would be a bad seal on the plunger either in the bowl or in the top of the housing. I picked the easiest to check first. and that's when I discovered the seal at the plunger closest to the frame rail was eaten up from the gas so I doubt the seal was made of Viton or any other gasoline resistant material.

After contacting the seller, to which they either used a Chinese to English translator or is a very poor speller, They offered to replace the current valve for a new one, they would not refund my money, so I guess I'm going to be stuck with a cheap knockoff that isn't going to work anyway. But in my mind I can probably practice on disassembling the cheap knockoff and if I can rebuild it with new Viton seals then I will be able to take the Ford OEM and rebuild that one.

 

I would not trust any chinese seller or chinese part
Look for new old stock OEM part in America
Or find a working one at a wrecking yard

 

Changed out all the O-rings over the weekend, still no start. I'm going to put a siphon hose down the front tank because the fuel gauge doesn't work on that, my thinking at this point is that the pump went bad while sitting or someone siphoned all the gas in the tank, which really wouldn't surprise me considering gas prices. I still haven't put gas in the rear tank yet, so I'm not sure if the switch even works. If the rain lets up I'm going to try to get to all this stuff this week. I'll be updating as I go along.

 

Crap ethanol left in my tank ate the sock on my pickup, could have dried yours out.

 

You never know. I thought I had at least half tank but not sure, too hot today 105 with the heat index.

 

Mine would not burn what was at 1/2 tank, it had to be flushed, the stuff was bad, only took 6 months sitting, mechanic had a heart attack.